help me choose the reflector/optics

[dsvilko]

I am building a 3x Creed R2 (star mounted) bike light and can't decide which reflector or lens to buy. I would very much prefer to by from DX site.
What is, in your opinion, the best (low cost) optics for the Cree emitters. Most of the reflectors have a narrow ~10 degrees spot. Is that not too narrow (I've got no experience with the high power bike lights - this will be my first).
All three emitters will be mounted on a 50x50x35mm heatsink (is that enough?) and driven with about 0.85A current (each) so all three will be pointing in exactly the same direction. What would you recommend?
http://www.dealextreme.com/details.dx/sku.1920 (narrow but good reviews)
http://www.dealextreme.com/details.dx/sku.1917
http://www.dealextreme.com/details.dx/sku.1916
http://www.dealextreme.com/details.dx/sku.1911 (looks promising)

All suggestions/experiences are very welcome!

 

[Zero_Enigma]

I wasn't too far off from your position about a year ago when I built my light.

I went with L2 Optics but I was using SSC U-bins at the time. Nevermind what LED I was using back then. What I have learned is when riding on the road 5 degree is good for on the road. 15 degree is good for a spot-flood.

I'm mostly a road rider myself tho I to take the paved trails at times. On the roads 2 x 5 degrees and 1 x 15 degree optic works very well. If you're making one for the helmet go with a tigher beam like 5 degree so you can spot lamp down the road.

You can check out my lighting on my webpage. The uber bright light is 4 x SSC P4 U-bin LED's with 2 x 5 degree and 2 x 15 degree. Combined with my 2x SSC P4 U-bin 5 degree helmet light I've got ~900lm's of lighting which cars really notice as they mostly slow down with the jaw drop look on thier face and I often hear a 'daaaaammmmnn' as they're driving by. :twothumbs

 

[yellow]

* the BEST reflector for an XR-E is Sandwich Shoppe's 19 mm (no matter if the normal or the XR-E version)
* the "original" fraen 8 deg. optic (the one with the white plastic holder) is the best cheaper focusing device
* the fraen plastic reflector is a bit less good than the optic
* cheap DX parts work like what they are
* forget multioptics

on a budget: Optic or fraen reflector
(why pay just a tiny bit less for the DX parts that give You crap results)
best of the best and accepting the cost: SS 19 mm

a small side note: the best way to use the light emitted from a led is a tight focusing.
Instead of a number of led using (and thus wasting) light with wide beam devices and giving parallel beams, it is much better to use 8 deg beams and position them a few degrees offset to the other - say 2-3 deg. spread in horizontal.

if f.e. two XR-E w. 8 deg. optics and making an oval main beam were compared to identical four XR-E w. oval beam optics, the 2 will still look brighter.
That has already been tested in the Luxeon age and therefore tight devices with non parallel beams has gotten standard with modders.
(and two SS 19 will eat any of the other setups. Damn they are so expensive)

 

[LukeA]

I wasn't too far off from your position about a year ago when I built my light.

I went with L2 Optics but I was using SSC U-bins at the time. Nevermind what LED I was using back then. What I have learned is when riding on the road 5 degree is good for on the road. 15 degree is good for a spot-flood.

I'm mostly a road rider myself tho I to take the paved trails at times. On the roads 2 x 5 degrees and 1 x 15 degree optic works very well. If you're making one for the helmet go with a tigher beam like 5 degree so you can spot lamp down the road.

You can check out my lighting on my webpage. The uber bright light is 4 x SSC P4 U-bin LED's with 2 x 5 degree and 2 x 15 degree. Combined with my 2x SSC P4 U-bin 5 degree helmet light I've got ~900lm's of lighting which cars really notice as they mostly slow down with the jaw drop look on thier face and I often hear a 'daaaaammmmnn' as they're driving by. :twothumbs

Those angle measures are half-angle measures. Just something to think about.

 

[dsvilko]

Thanks guys!
So, the consensus is that the narrow (10 or less) beam is actually not bad at all. I know that there are better optics out there for a higher price but I would really like to build this light on the budget. On DX I currently have in my shopping cart 4 Cree XR-E R2 (WG) leds, 4 regulator boards, 5 lenses (for Cree emitters) and a bike mount - all for $41. With that I plan to build one 3xR2 light and also modify the generic bike light I currently have, replacing it's 2.4W halogen bulb with the fourth Cree. Each light will be powered with the integrated 4xNiMH pack (I am currently not in a habit of taking long night rides). That way I should be able to get close to 1000lm! In reality it will probably be around 700lm, but in any case, a small step up from a 2.4W halogen
I think I'll go with the http://www.dealextreme.com/details.dx/sku.1920 optics. It's got very good reviews. Again, I know there are better optics and I do appreciate your suggestions but for me, even $40 seems a lot of money to spend on a bike light.
Unfortunately, all the three leds of my 3xR2 light will have to point in the same direction as I am mounting them on a flat heatsink (is a 50x50x35mm heatsink enough of a cooling for three Cree stars @0.9A?). If I decide that I need more flood light, I'll probably use a tape over a lens or two.
Thanks again for sharing your experience!
A week ago I was only dimly aware that there exist leds more powerful than a generic 5mm 15cd. Then I discovered DX site and was shocked by the low price of these high power leds. Now I can't stop reading about the subject! This stuff is really addictive! There should be a warning

 

[Zero_Enigma]

Forgot to list my webpage.

http://www.flickr.com/photos/49184877@N00/page4/

Check the previous and forward pages for more bike lighting. I've got specs, timings, and beam shots.

Quad-damage is awesome If you need some help I can help out when I can. Only Cree optics I have are the smooth and textured alum. reflectors for my Cree Q5's which I've not used yet. You'll see the Q5's mounted on that massive heatsink when I was blasting about 10 LED's.

Enjoy and sunglasses are sold after the viewing. LOL

 

[mkrabach]

I have used the DX-1920 in one of my prototype bike lights.
http://www.kayakaccessri.info/krabachwebsite/bike_light/bike_light_project/proto14.html
I find that they are a little too narrow for bike riding. I like another DX tri-optic lens that gives me a little wider beam. All the beam shots are on this page. http://www.kayakaccessri.info/krabachwebsite/bike_light/bike_light_project/light.html
There is alot of other information on other lens and optic types and beam shots for all of them. Look at the table of contents. All the components are listed in the 'Summary Table and Parts Sources' page. I find the cheap DX optics quite adequate.

 

[dsvilko]

I have used the DX-1920 in one of my prototype bike lights.
http://www.kayakaccessri.info/krabachwebsite/bike_light/bike_light_project/proto14.html
I find that they are a little too narrow for bike riding. I like another DX tri-optic lens that gives me a little wider beam. All the beam shots are on this page. http://www.kayakaccessri.info/krabachwebsite/bike_light/bike_light_project/light.html
There is alot of other information on other lens and optic types and beam shots for all of them. Look at the table of contents. All the components are listed in the 'Summary Table and Parts Sources' page. I find the cheap DX optics quite adequate.

Thanks! That was extremely informative! So, the sku.1920 may not be such a good choice after all. Unfortunately, I have already ordered it Will I be able to remedy the narrow beam with a Scotch tape or a similar low-end diffuser?
Also, one more question if I may... will a 50x50x35mm CPU heatsink be enough for a three Cree 3W leds or should I also add a small fan?

 

[mkrabach]

The beam is narrow, but it still is a good beam. From my fussing around with diffusers, the only ones that I found good are the ones that mate with the L2 optics. As an experiment I just now tried taping (clear scotch tape) the diffusers used on prototype 2 on the front of the prototype 14. Not too bad but you would have to file the diameter smaller on the diffusers. Probably not worth the effort and ordering just the diffusers (S&H costs) to get the effect you want. I tried the Scotch Matte Finish Magic tape on the prototype 14 and it was not too bad with the tape over the two outer LEDs and the center one uncovered. Although the effect is more of a blurring of the beam than diffusing it. The L2 optics are actually clear, but because the surface texture is finely embrossed, it appears to you as a matte surface. So a beam is passing through tiny prisms is diffused with a 15% (or so I have heard) loss. The Scotch tape appears to decrease the brightness by at least 20-30%. Try it out that way and if not to your liking, you still have a nice roll of tape.

As far as the heat sink, it probably would be ok when riding. You can see the size of the heat sink I used in Prototype 2. It gets up to about 130F (using an IR temperature meter) in still air (65F) in the house. But is cool when riding. I have a similar CPU heat sinks 50x50x15mm size that I was considering using, but mounting to a handlebar clip was a problem, so I did not use it. Instead I went with the power transistor heat sink, cut in half. Then I started using the angle aluminum stock to simplify the constructions. I would suggest try out the CPU heat sink and since it originally had fan mounted on the top, you could use that fan if needed. The fan will be 12 v so if you power the 3 LEDs from a 12v battery, no problem. But I dont think you will need the fan. If you use a pot to control the brightness, that will also control the heat. So for slow riding where your light is getting hot, just reduce the light output.

 

[dsvilko]

Thanks again! Your site has been most informative, specially regarding the beam patterns. I'll certainly try to diffuse the light somewhat though I am still not certain how.

 

[FrontRanger]

Thanks guys!
So, the consensus is that the narrow (10 or less) beam is actually not bad at all. I know that there are better optics out there for a higher price but I would really like to build this light on the budget.

I use a (nominally) 6-degree optic on one of my lights and find myself wanting it even narrower in many cases. In my opinion, optics are not the place to save money in a home-brew light. If it means the difference between being satisfied with the output or not, then a few dollars difference is just not worth the time you spend planning and building it.

for me, even $40 seems a lot of money to spend on a bike light.

Although $40 is much more than a $4 Walmart bike light, the price of good bicycle lighting is still much cheaper than a car or a trip to the ER. That's my perspective, anyway.

On DX I currently have in my shopping cart ... 4 regulator boards

Why 4 boards? I'm guessing Buck regulator, so 4x NiMH is not enough battery voltage to run 3x LED in series, so running one LED per board, 3x of those in parallel? Also, depending on efficiency of drivers, your 3x R2 at 0.85A each will burn something like 10 or 11 W. You didn't say what your battery capacity is, and you also said you don't plan to ride for very long at one time, but are you sure you have enough capacity? (Maybe you're already satisfied with this, but it can't hurt to ask.)

Unfortunately, all the three leds of my 3xR2 light will have to point in the same direction as I am mounting them on a flat heatsink

Even if you can't mount the LEDs independently, can you grind an angle into your heatsink? Or can you put some thermally conductive material beneath two of them to create an angle?

Best of luck!

 

[dsvilko]

I use a (nominally) 6-degree optic on one of my lights and find myself wanting it even narrower in many cases.

So, there is a chance I could like this 8-degree? It had really good reviews, even from mountainbikers though I must say that this http://www.kayakaccessri.info/kraba...bike_light_project/driveway_beams/proto14.JPG beam looks too narrow.

Why 4 boards? I'm guessing Buck regulator, so 4x NiMH is not enough battery voltage to run 3x LED in series, so running one LED per board, 3x of those in parallel? Also, depending on efficiency of drivers, your 3x R2 at 0.85A each will burn something like 10 or 11 W. You didn't say what your battery capacity is, and you also said you don't plan to ride for very long at one time, but are you sure you have enough capacity? (Maybe you're already satisfied with this, but it can't hurt to ask.)

You are right. I will be running the leds in parallel with one driver for each led. I have also estimated the overall power at about 11W. With a set of Sanyo Eneloop batteries I should be able to get 45 minutes with all the 3 leds turned on. With only one led turned on the runtime should be over 2 hours. I am mostly riding in the city so for the most roads I really don't need that much light (only enough to be seen) but there are a few darker roads that could use a bit more light.
Here is what the light will look like:

It won't win any beauty contests but it will be tiny for such a strong light with the integrated batteries. The batteries will stick out slightly to help with the cooling and for the easy battery pack change. I will use a 4AA battery holder with a '9V battery' connector at the end and the matching connector glued inside the box so connecting the battery pack will be as simple as sliding it inside so I can always carry a spare pack for the longer rides. With two packs (maybe one of them 2700mAh) and 2 leds turned on I should get almost 3 hours of runtime.

Even if you can't mount the LEDs independently, can you grind an angle into your heatsink? Or can you put some thermally conductive material beneath two of them to create an angle?

I am afraid that the heatsink is not thick enough for grinding and that I have no way of grinding a flat surface at such a small angle. Would it be possible to angle only the optics slightly?
I am guessing that the narrow optics would work much better if I managed to mount the light as low as possible (over the wheel and not on the handlebar)?
Thanks for your help!

 

[FrontRanger]

So, there is a chance I could like this 8-degree? It had really good reviews, even from mountainbikers though I must say that this http://www.kayakaccessri.info/kraba...bike_light_project/driveway_beams/proto14.JPG beam looks too narrow.

It's hard to say without seeing it in person. Beamshots help, but cameras aren't eyes. Many DIY-ers simply experiment with the optics until they get what they want. Not a nice thing to hear when you want to buy once and minimize expense, but there it is. One thing to beware of is that the beam (or half-beam) width doesn't tell you that much about the beam; it's possible to make two very different beam patterns that have the same half-power angle.

I am afraid that the heatsink is not thick enough for grinding and that I have no way of grinding a flat surface at such a small angle. Would it be possible to angle only the optics slightly?

You can try it, since it's easy and cheap, but generally you don't want to angle the optic with respect to the LED; better to move them both together. If that doesn't pan out, what about putting something beneath the star to create an angle between it and the heat sink? Aluminum foil and epoxy? Never tried it, just a thought.

I am guessing that the narrow optics would work much better if I managed to mount the light as low as possible (over the wheel and not on the handlebar)?
Thanks for your help!

That depends on the beam pattern. Some European production lights (e.g., from Busch & Müller) have narrow, carefully formed beams that look trapezoidal on surface perpendicular to the light, but become rectangular when projected at a sharp angle (as happens on a bicycle!). Those can do well when mounted low, helping highlight road irregularities. But for broader, less well-defined beams, a less acute angle (meaning, a higher mount) is probably better, since it puts more light on the ground and less into outer space or oncoming drivers' eyes. I either clamp lights to the bar, or suspend them below the bar or the stem.

 

[dsvilko]

Thanks FrontRanger!
As I will often ride my bike in a heavily populated area I certainly wouldn't want to blind the other drivers. From that perspective mounting the light higher makes sense. I still don't know how to solve the probably too narrow beam of the sku.1920 optics.
Does anyone have any experience with the http://www.dealextreme.com/details.dx/sku.4626 optics? Can they be fitted to the Cree star emitter? A beamshot would be very welcome.

 

[FrontRanger]

Does anyone have any experience with the http://www.dealextreme.com/details.dx/sku.4626 optics? Can they be fitted to the Cree star emitter? A beamshot would be very welcome.

No, but I have this one, which I think is the 15-degree version of the same type as DX sku 4626. I would not get the 30-degree. Maybe 1x 15-degree and 2x 5-degree on a 3x LED setup.

These fit without modification for SSC P4 or Luxeon. A reviewer on your link says he's modded them for Cree.

 

[dsvilko]

No, but I have this one, which I think is the 15-degree version of the same type as DX sku 4626. I would not get the 30-degree. Maybe 1x 15-degree and 2x 5-degree on a 3x LED setup.

There has been a slight change of plan. I am going to build two lights, each with 2 Cree R2 emitters and their own 4xAANiMH battery packs. One will be pure spot (with Cree 8-deg optics - DX 1920) aimed far and the other will be pure flood aimed maybe 2m from my bike. As I see it, the problem with the mixed optics in the same light is that you lose a good part (>30%?) of your flood light into the sky, also blinding incoming traffic in the process. This way I get about 800lm with very little above the horizon light loss.
30-degree optics (according to a DX review it's closer to 15-deg spot with 40-deg flood) aimed 2m from the bike should not be too floody. At that distance the spot from that lens should be 0.7m wide and the flood 1.8m wide which sounds good - almost no light should escape into the sky.

With two lights the runtime (Eneloop batteries) should be:
1 hour @ 800lm
2.5 hours @ 400lm
5 hours @ 200lm

Also, with only two leds per heatsink, I don't think I'll be needing the cooling fan. I can also lend one to my girlfriend when we go biking together.

 

[Cemoi]

you lose a good part (>30%?) of your flood light into the sky

Why not use elliptical beam optics to avoid this?

 

[dsvilko]

Why not use elliptical beam optics to avoid this?

I don't see how that would help. If I am not mistaken, the ideal beam pattern would be an isosceles trapezoid with vertical intensity gradient but I am not aware of such a lens/reflector for the high power leds. At the upper end of the beam you want a high intensity with a sharp cut-off (for a far reach and not to blind the incoming cars) but you still need a lot of spill for near road illumination. If the spill is symmetrical in relation to the central spot then you lose most of the upper part of the spill. The logical solution is to have an independent spot and flood lights and to aim the flood a lot lower than the spot. That way I can have an excellent throw with a relatively sharp cut-off and also an excellent near-road visibility with very little side and above-the-horizont light loss. With elliptical beam you would need a far greater intensity to get the same amount of both near road and far road illumination (maybe as much as two times more!). On the other hand, the elliptical beam has a wider throw so it could be better for navigating around sharp bends. As I ride mostly on straight roads and often where there is a lot of traffic I prefer a far throw with a sharp cut-off to a good side spill. In the end it comes down to how and where you ride.
I'll certaily post some beamshots when the lights are done. The current regulators are on back order again so it could be a few months for all I know